This project is concerned with behavioral analyses of information transmission within the spinal somesthetic pathways. The approach is to obtain psychophysical thresholds before and after a variety of spinal lesions have been administered to monkeys. In addition, the investigations of monkeys are supplemented with human psychophysical investigations, using similar stimulus manipulations, to efficiently define interesting phenomena of somatosensory coding and to specify the degree to which the sensitivity of the monkeys corresponds to that of humans. The proposed studies deal with 3 major classes of somatosensory input: pain, proprioception, and touch. In the first instance, we will define the importance of descending spinal pathways for pain control by morphine. The investigation of touch and proprioception will concentrate on temporal coding, to compliment our previous studies which have emphasized spatial coding. We will test the effects of spinal lesions on discriminations of touch duration and limb position during movement. In each study, we will administer multiple spinal lesions until deficits are obtained, and the extent of functional recovery following these spinal cord injuries will be carefully plotted.